Non-tuberculous mycobacteria (NTM)

What is Non-tuberculous mycobacteria (NM)?

NTM is a group of bacteria, normally found in soil and water and some domestic and wild animals, that can cause severe lung disease. NTM represent over 180 different species and subspecies, most of which do not cause human disease except in susceptible individuals who has pre-existing lung conditions (COPD, emphysema,cystic fibrosis, bronchiectasis) or those who has immune deficiency conditions (HIV/AIDS and those on immune-suppressants).

Some develop an NTM infection when they inhale the bacteria in the air or water mist, or when they drink water containing NTM. In most people, the NTM organisms are cleared from the lung naturally and do not cause infection. But in susceptible people, the organism infects the airways and lung tissue leading to disease. It causes inflammation in the respiratory system. NTM is a slowly progressive and destructive lung disease characterized by cough, shortness of breath, fatigue, and weight loss. Severe NTM lung disease can significantly impact one's quality of life. Death directly related to NTM lung disease is rare. There are also reports of NTM infections involving other organs like skin, soft tissues and bone/joints.

NTM does not cause tuberculosis (TB), and unlike TB, which is spread from person to person, NTM is not contagious. Diagnosing NTM can be difficult because symptoms may mimic other lung conditions.

Risk factors for developing NTM Lung disease

Pre-existing Lung disease: Many people with NTM lung disease have another underlying lung problem like COPD, bronchiectasis, emphysema, cystic fibrosis, previous infections such as tuberculosis.

Age: More common in older people.

Immune deficiency: Illnesses that affect the immune system, like Sjogren’s disease and rheumatoid arthritis, HIV/AIDS, may increase the risk of NTM infection. Also drugs that can weaken the immune system, such as steroids can also increase the risk of NTM infection.

Slender Caucasian women: Some women who have features like being tall and slender, having a curved spine, abnormalities of the breastbone, and mitral valve prolapse appear to have an increased risk of developing NTM disease.

Esophageal disorders: People with acid reflux and other disorders of the esophagus can increase the risk of NTM lung disease due to spillage of gastric contents into the lung.

Environment: Exposure to NTM in the environment can result in infection. High-risk sources include indoor hot tubs and pools and exposure to soil.

Symptoms of NTM

Not everyone with NTM lung disease has symptoms, but those with more severe infection, will have symptoms. NTM can affect all organs of the body but it primarily affects the lungs. Symptoms typically progress slowly and they get diagnosed only years later when their symptoms start to show. The symptoms are:

Blood in sputum (hemoptysis)

Cough

Fever

Lack of appetite

Loss of energy/fatigue

Night sweats

Weight loss

Shortness of breath on exertion

Diagnosis of NTM

​Diagnosing NTM may be difficult because its symptoms often resemble other lung conditions, such as tuberculosis (TB). It is important to determine if the infection is TB or NTM because the treatment is different. If a patient does have NTM, it is important to determine which type of bacteria is causing the condition in order to direct the proper treatment. Diagnosing NTM includes:

Taking a complete medical history

Physical examination

Lung function tests

Chest X-ray: baseline investigation

Computed tomography (CT) scan: a more detailed scan which may show small nodules (sometimes referred to as "tree-in-bud" because of their branch like appearance) and also identify cavities/abscesses in the lung, which represent a more destructive form of infection.

Sputum culture : Several sputum cultures are often necessary as one positive test does not always mean disease is present. It is also necessary for treatment plan to see which medications are suitable.

Bronchoscopy: This test involves passing a flexible fiberoptic scope into the lungs to obtain fluid and sometimes tissue samples to aid in diagnosis. ​ ​

Treatment of NTM

Most of the nontuberculous mycobacteria are naturally resistant to common antibiotics. The treatment regimens recommended vary depending on the species isolated from the culture and the results from drug susceptibility testing. Some of medications used to treat NTM are also used to treat tuberculosis (TB). To overcome drug resistance, patients may need to take several different antibiotics at the same time.

Usually the regimen includes three antibiotics, initially through intravenous in combination with oral and later by oral. These medications may have side effects thus close monitoring with visual tests, audio tests and blood tests are important. Treatment may be as long as two years. The goal of treatment is to achieve “negative” sputum cultures and maintain that for 12 months before stopping.

The most common NTM organisms involved in human are M. avium complex, M. kansasii and M. abscessus. M. kansasii is easier to treatas it can be killed with only three anti-TB medications. Other organisms such as M. avium complex, M. chelonae and M. abscessus are more difficult to treat, three to five medications may be needed.

​Some patients may need surgery to remove the most damaged areas of the lung. Surgery can be performed using VATS (video-assisted thoracoscopic surgery).

A complete cure can be expected with some NTM species but not with others. Re-infection is common despite treatment.